I'm just curious to hear from those with personal experience. I'm a performance enthusiast, but I must admit, I want to keep my gas mileage, as that is what I bought my Yaris S-Type for. I also own a 1993 Camaro Z28 w/ ~450hp, so I don't plan to modify my Yaris S-Type with anything too extreme, because as I said before, gas mileage is important. I know some mods shouldn't affect gas mileage, and could, in fact, possibly improve it. When I started modding my Camaro many years ago, the first mods were simple bolt-ons: headers, exhaust, cold air induction, etc. These mods seemed to not affect my mileage at all, and in fact, since it helped the engine breath easier and run more efficiently, my gas mileage actually IMPROVED.

So my question is, what can I do, in terms of mods, for my S-Type sedan that will improve performance but won't affect gas mileage??

Same stuff- Lightweight pulley, CAI, lighter wheels... I think once you get to exhaust, stay cat-back or I would imagine you'll lean out the engine too much and start losing performance without adjusting your air-fuel mixture in the injectors and then you are richening it, using more gas and defeating your purpose.

I think CAI's reduce fuel economy, though not by much. The whole idea is to add colder air, which causes the injectors to use slightly more fuel (because gas doesn't atomize well in colder temps), thus an increase in power.

A short ram intake, on the other hand, will allow the engine to breath easier than the CAI (less pipe to travel through, thus less drag), without requiring more fuel. Not as powerful as a CAI, but great throttle response (supposedly).

A lot of people swear their CAI gets better mileage, better low end, and better top end all at once, but I'm pretty sure that's all in their heads. If it was such an improvement in every respect, I'm pretty sure the car manufacturers would have picked up on it by now and it would be standard tech.

~YR

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Performance mods come in different flavors. One you may not have considered is a solar trickle charger, which also helps FE.

By keeping the battery topped off during the day and then continually contributing to its charge level while running around, even just in a minute amount, is that much less time the alternator needs to place a load on the engine every day.

Any energy not used by the alternator is that much more of the "natural" energy the engine produces that is available to you, and you are saving fuel because the engine doesn't have so much of an external load on it.

Another mod that becomes a performance mod by proxy is an engine block heater (EBH), which also makes a noticeably positive impact on FE.

How this becomes a performance mod is in its engine protection. Once you start using an EBH it's a rare day that you perform a "cold start", which is hard on an engine regardless of what oil or additives are used. By keeping the engine healthier and happier it will keep putting out at 100% for much longer.

This also saves lots of fuel because the days of the ECU/engine running extra rich at extra high RPM in a race to get the fluids and emissions system warm after a cold start will be gone.

Performance mods come in different flavors. One you may not have considered is a solar trickle charger, which also helps FE.

By keeping the battery topped off during the day and then continually contributing to its charge level while running around, even just in a minute amount, is that much less time the alternator needs to place a load on the engine every day.

Any energy not used by the alternator is that much more of the "natural" energy the engine produces that is available to you, and you are saving fuel because the engine doesn't have so much of an external load on it.

Another mod that becomes a performance mod by proxy is an engine block heater (EBH), which also makes a noticeably positive impact on FE.

How this becomes a performance mod is in its engine protection. Once you start using an EBH it's a rare day that you perform a "cold start", which is hard on an engine regardless of what oil or additives are used. By keeping the engine healthier and happier it will keep putting out at 100% for much longer.

This also saves lots of fuel because the days of the ECU/engine running extra rich at extra high RPM in a race to get the fluids and emissions system warm after a cold start will be gone.